Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque

H, W = map(int, input().split())
w = "#"*(W+2)
white = 0
S = [w]
for _ in range(H):
    wwww = input()
    white += wwww.count(".")
    S.append("#"+wwww+"#")
S.append(w)

m = [[10**10]*(W+2) for _ in range(H+2)]

q = deque([[1, 1]])
d = ((-1, 0), (0, -1), (0, 1), (1, 0))

m[1][1] = 0

while q:
    y, x = q.popleft()
    p = m[y][x]
    for dx, dy in d:
        xx = x + dx
        yy = y + dy
        if S[yy][xx] == "#":
            continue
        if m[yy][xx] > p+1:
            m[yy][xx] = p+1
            q.append([yy, xx])

if m[H][W] == 10**10:
    print(-1)
else:
    print(white-m[H][W]-1)